Unfortunately, larger tech companies in the US have become increasingly (in the last 5-10 years) political inside and a desire to ship things fast has ultimately meant building extremely high performance scalable infra that's foundational enough to be OSS-able is just not a priority since compute is cheap enough and it's not worth the cost of generalizing it to make it OSS. It's just very hard to pitch these kinds of investments. Documentation follows this pattern-- engineers just don't get promoted or rewarded for writing documentation and with IC's constantly being pushed to deliver faster and faster it just won't take priority. And that's a big problem.

In short, it's my impression it's an engineering culture problem in large part caused by bad leadership at the types of companies where these projects could be possible.